How to use the dataclasses.field.metadata.get function in dataclasses

def read__query(self):
        fields_to_select = {}
        to_group_by = []

        for field_name, field in self.resource.fields.items():
            model_field = field.metadata.get("model_field")
            if field.load_only:
                continue

            if model_field is None:
                raise Exception(
                    f"{self.resource.Meta.name}.{field_name} field must have "
                    f"'model_field' argument"
                )

            if isinstance(field, ToMany):
                fields_to_select[field_name] = sa.func.array_remove(
                    sa.func.array_agg(model_field), None
                )
            elif isinstance(field, ToOne):
                fields_to_select[field_name] = model_field
            else:

def field_ops(field: Field) -> Iterator[str]:
    yield field.name
    for op in field.metadata.get(OPS, ()):
        yield f"{field.name}:{op}"

def wrapper(cls):
        cls = dataclass(cls)
        cls._csv_file = csv_file

        cls._csv_id_field = None
        cls._csv_parent_field = None
        cls._csv_index_field = None
        cls._csv_node_list_fields = []
        cls._csv_node_fields = []
        cls._csv_fields = {}

        for field in fields(cls):
            csv_type = field.metadata.get(FIELD_METADATA_CSVMODEL_TYPE, None)
            if csv_type == 'id':
                assert cls._csv_id_field is None, "Already has an ID field"
                cls._csv_id_field = field
            elif csv_type == 'child_parent_node':
                assert cls._csv_parent_field is None, "Already has a parent ID field"
                cls._csv_parent_field = field
                cls._csv_node_fields.append(field)
            elif csv_type == 'child_index':
                assert cls._csv_index_field is None, "Already has a list index field"
                cls._csv_index_field = field
            elif csv_type == 'children_list':
                cls._csv_node_list_fields.append(field)
            elif csv_type == 'reference':
                cls._csv_node_fields.append(field)